A typical radio frequency identification (RFID) tag has a memory configured to store data, such as data that uniquely identifies the tag among a plurality of RFID tags. An RFID reader can be used to communicate with RFID tags over a radio link. Thus, the identity of the tag and the object labeled by the tag can be determined by the RFID reader in an automated process.
In a typical RFID system, an RFID reader is configured to interrogate the tags via radio frequency electromagnetic waves. The RFID reader broadcasts commands using a beam of electromagnetic wave. In response to the interrogation signals from the RFID reader, an RFID tag can be selected to produce a radio frequency response signal.
An RFID tag may be passive, semi-passive or active, depending on the power source of the RFID tag and how the response from the RFID is generated.
A passive RFID tag does not have an internal battery or power source. A passive RFID tag operates using the power drawn from the interrogating electromagnetic wave. A passive RFID tag provides responses through modulating the interrogating electromagnetic wave backscattered by the tag.
A semi-active RFID tag operates using the power drawn from its internal battery or power source. A semi-active RFID tag provides responses through modulating the interrogating electromagnetic wave backscattered by the tag.
An active tag that has an internal battery or power source, using which a separate transmission signal is generated to provide the response. The response carrier signal is generated independent from the interrogating electromagnetic wave.
Radio frequency identification (RFID) tags are used in a variety of applications, such as tagging vehicles on toll roads, tagging shipping containers, quality control on assembly line conveyor belts, and monitoring tactical military equipment maneuvers, etc.